Question about Configuration VLAN

hello everyone, i m now in the process of vlan configuration.

i found the trunk link in a switch, e.g. port 25, no matter how many vlan i assigned it, it is always the membership of vlan 1(default vlan) and I must set it untagged(only on vlan 1), or i can not ping the switch.

is there anyone can explain for me? thank you.

A trunk port is typically set for VLAN 1. For Cisco switches, this should be automatic. What makes it a trunk port is not what VLAN it belongs to, but the characteristics of it, and that is configurable. On a Cisco switch (I presume this is the equipment you are working with) you would issue the commands on your trunk port to-be:

switch(config)#interface fa0/25
switch(config-if)#switchport trunk encapsulation dot1q
switch(config-if)#switchport mode trunk

Wherever your trunk port is going (it's uplinked switchport) ensure that it is also configured as a dot1q trunk.

As for why you can only ping your switch if it is on VLAN 1, your IP address is probably configured on interface vlan 1. Therefore, if your trunk port is not configured correctly, it would only forward traffic on its own VLAN -- 1.

thanks, jwj. u r right. when i try to ping my switch, i connected to another switch, which assigned me to vlan1, that's why i can't get response from the switch.

by the way, my switches are 3com, cisco costs too much